Subsea Experience Gained At Zakum

Abstract

INTRODUCTION Following discussions between the British Petroleum Co. Ltd. (BP) and Companies Françoise des Petioles Society Anonyms (C.F.P.) during 1968, the decision was made by the Board of Abu Dhabi Marine Areas Ltd. (ADMA) to prepare a program for installation and evaluation of an integrated subsea production system. The project known as the Zakum subsea production scheme covers the period Aug. 1969 to April 1972, in which time equipment-and techniques developed by BP, CFP, oilfield manufacturers, and service companies were operated and evaluated SUMMARY The objectives of the scheme were:to achieve production from the well at Zakum 39 using subsea methods, andto gain experience of subsea production methods and equipment so as to evaluate their practicability and relevance to future operations. The range of equipment and techniques investigated covered most aspects of subsea production. In addition to primary production equipment (wellhead, valves, actuators, flowlines), a range of ancillary equipment and support services were also included (separators, underwater power sources, instrumentation, diving services, surface support vessels). The conditions at Zakum for operating a subsea production system were not difficult as the water depth was only 22 m, and this allowed easy diver access. A contract diving service provided the support to the subsea production group, which comprised production, petroleum, and instrumentation engineers who had been trained to dive. A great deal of experience relevant to subsea operations in deeper water and under more severe offshore conditions has also been provided under the scheme. During the period Aug. 1969 to April 1972, the major work effort was as follows. (Available in full paper) MAIN CONCLUSIONS The following conclusions are presented as a result of the experience gained during the period of operation and evaluation of the Zakum subsea production scheme. General The scheme confirmed that there appears to be no major difficulty in producing from a subsea oil well in water depths up to 100 m apart from that of access. With the developments taking place there appears to be no reason why one cannot operate deep water subsea oil wells but the equipment undo servicing concepts will differ from the shallow-water operations. The transport of oil by subsea pipeline is now feasible in water depths up to 150 m and developments are in hand to extend this depth. The processing of oil (separators, pumps, storage, etc.), however, must be regarded with some considerable reserve, and it is considered unlikely that complete subsea production and processing systems (as opposed to those with surface intervention) will be introduced in the near future. These general conclusions are supported by the experience of other users of subsea equipment. Well Production and Maintenance No major problems were encountered in the use of the subsea wellhead at Zakum, and steady production was maintained throughout the period of operation and evaluation. Consequently, it is believed that a practical subsea well production system could be developed, which in a simple form should be reliable and suitable for operation in water depths within easy diver access.